At present, insulin is clinically used as a treatment for diabetes in the form of an injectable formulation, and in most cases, it is self-administered by a comparatively simple subcutaneous injection. However, due to the characteristics of this type of injection formulation, the patient is required to self-administer one to four times a day before meals, for life. This troublesome procedure is one of the many problems associated with the treatment of diabetes. Besides insulin, many pharmaceutical peptides are also administered by injections, and there is an ongoing development of dosage forms for convenient administration.
Formulations for nasal administration, in particular, have been proposed to overcome the difficulties associated with administration. For example, a dosage form of insulin formulation, which uses crystalline cellulose as a base and has 90 wt % of particles in the diameter range of 20 to 150 μm, is described in Examined Published Japanese Patent Application No. (JP-B) Sho 62-42888. Considering that for this formulation, “physiologically active polypeptides are preferably water-soluble for nasal mucosal absorption,” the Example of this publication discloses that compositions having 90 wt % or more of particles with a diameter of 75 to 149 μm are obtained by: dissolving insulin in aqueous 0.1 N HCl and freeze-drying; mixing the thus-obtained soluble insulin powder with crystalline cellulose; and sifting.
In comparison with compositions in the above-mentioned JP-B Sho 62-42888, Unexamined Published Japanese Patent Application No. (JP-A) Hei 10-59841 (corresponding to EP-A1-943326) discloses compositions which demonstrate excellent nasal absorption and increased maximum blood concentration with highly hydrophilic pharmaceuticals, highly lipophilic pharmaceuticals, and high molecular weight peptides. According to this publication, the above-described effect can be achieved by actively using a water-absorbing and gel-forming base, such as hydroxypropylcellulose, in combination with a crystalline cellulose aggregate comprising particles with a diameter greater than 150 μm, which is contrary to what JP-B Sho 62-42888 suggests.
However, the present inventors are not aware of any information on the practical application of formulations for nasal administration, in particular, those for nasal administration of polypeptide hormones including insulin as described in these prior arts.